Diurnal variations in cosmic ray intensity caused by high latitude magnetospheric-ionospheric current systems

Cosmic ray intensity measurements obtained with the neutron monitors at Thule (geomagnetic latitude, 84.8°) and McMurdo (geomagnetic latitude, −79.9°) in 2007–2009 were used to test the effect of the magnetic field generated by magnetospheric currents flowing along geomagnetic field lines in the high latitude region on cosmic ray intensity. The existence of such a relation in a region where the geomagnetic field lines are virtually radial should revise our concept of the unimpeded access that cosmic ray particles have to the Earth’s atmosphere.     

Time fluctuations of charged and neutral cosmic-ray component fluxes as measured in the region of the brazilian magnetic anomaly

Summary Measurements of charged particles, gamma emission and neutrons were fulfilled on balloon in the region of the Brazilian magnetic anomaly on 8 November 1991. The flight lasted approximately 18 hours, including 15 hours on the ceiling at the height of 32 km just during the beginning of the recovery phase of the moderate geomagnetic storm. The main conclusion from the analysis of the obtained experimental data is the following:a) the fluxes of charged and neutral particles were measured and are in agreement with the data of previous works for the close values of geomagnetic cut-off rigidity;b) no sporadic increases of charged- and neutral-particle fluxes were recorded;c) the pulsations of charged particles, gamma-rays and neutrons with characteristic time of ≈ 30 min were found. The sporadic pulsations of charged particles and gamma-rays with shorter periods were observed too. But later pulsations were absent in the neutron flux data. This points to the magnetospheric origin of the observed phenomenon.     

First experimental observations of neutron bursts under thunderstorm clouds near sea level

The connection of short-term neutron bursts near sea level with the electric and geomagnetic atmospheric fields during thunderstorms in 2009–2011 has been experimentally studied. The data from the cosmic-ray spectrograph named after Kuzmin, an electrostatic fluxmeter, and a three-component fluxgate magnetometer in Yakutsk have been analyzed. It has been shown that short-term (no longer than 4 min) neutron bursts are due to negative lightning discharges. The bursts are detected at the ground level 1–3 km below thunderstorm clouds. In this case, the neutron flux is about 4 × 10⁻³ cm⁻² s⁻¹. The minimum energy of the neutrons that are efficiently detected by the monitor is about 10 MeV. It has been found that short-term neutron bursts are detected when the electric field strength reaches a threshold value of −16 kV/m.     

Cosmic-ray intensity increase observed on September 29, 1989: the Chilean neutron monitor data

Summary Data obtained in Chile with the standard neutron monitor (Santiago: 6 NM-64; geomagnetic cut-off rigidity: about 11 GV) are reported for the ground-level solar cosmic-ray event registered on September 29, 1989. Possible studies connected with such a rare event are suggested to understand even more solar-interplanetary-terrestrial relations.     

Effect of strongly perturbed magnetosphere on the cosmic-ray cutoff rigidity

Comprehensive determination of the cosmic-ray cutoff rigidity in strongly perturbed periods has been performed for a number of stations located at different latitudes. To calculate the geomagnetic cutoffs by tracing the trajectories of cosmic-ray particles in the magnetic field of the magnetosphere, the model of strongly perturbed magnetosphere was used [1–3]. The diurnal anisotropy of the geomagnetic cutoff rigidity in the minimum of D _st variation in the geomagnetic field has been estimated.     

Energetic neutrons and gamma rays measured on the Aryabhata satellite

An experiment to measure energetic neutrons and gamma rays in space was launched in the first Indian scientific satellite,Aryobhata, on April 19, 1975. From this experiment, the first measurements in space of the Earth’s albedo fiux of neutrons of energy between 20 and 500 MeV have been made; the values obtained for two mean geomagnetic vertical cut-off rigidities of 5.6 and 17.0 GV are (6.3±0.4)×10⁻² and (1.4±0.3)×10⁻² neutrons cm⁻² sec⁻¹ respectively. These measurements confirm that protons arising from cosmic ray albedo neutron decay, can adequately account for the protons in the inner radiation belt. Observations on gamma rays of energy between 0.2 and 24 MeV have enabled the determination of the total background gamma ray flux in space as a function of latitude. This in turn has permitted useful information on the diffuse cosmic gamma rays. We have also observed four events that showed sudden increases in the gamma ray counting rates between 0.2 and 4.0 MeV. Observational details of these events are given.     

North-South anisotropy during the quasi-stationary modulation of galactic cosmic rays

Summary High-speed solar-wind streams coming from coronal holes produce, in the interplanetary space, a quasi-stationary modulation of galactic cosmic rays. The Rome cosmic-ray group has analysed this modulation taking into account not only the charged-particle isotropic intensity but also the North-South anisotropy (A _NS), derived from ground-based measurements. The obtained results for the period October 1964–December 1987 are summarized. Data from the Bartels solar rotation no. 2034 (May 23–June 18, 1982) are used to illustrate theA _NS phenomenology. Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990.     

Semiclassical Resolvent Estimates for Trapping Perturbations

We study the semiclassical estimates of the resolvent of a self-adjoint operator L(h) in the space of bounded operators . In the general case of long-range trapping “black-box” perturbations we prove that the estimate of the cut-off resolvent implies the estimate . Received: 15 November 1999 / Accepted: 1 March 2000     

16-month periodicity of cosmic-ray intensity

Summary Data from four neutron monitors, Climax (1953–1976), Deep River (1964–1977), Mt. Norikura (1957–1983) and Tokyo (1970–1983) are analysed. Power spectra reveal peaks at frequency 1c/16 months for all the stations. Harmonic analysis for the 16-month period is performed after eliminating the long-term solar-cycle variation. There is general agreement in the phases of the mean vectors for various neutron monitors. The amplitude averaged over all the four stations is 0.41±0.01, while it is higher for the two stations having lower cut-off rigidity as compared to that of the other two. The vectors are seen to become more consistent in phase for periods of minimum solar activity than those for maximum-activity period. The summation dials reveal abrupt changes in the directions of the 16-month wave vector corresponding to the reversal of polarity of the solar magnetic field. Comparison of the 16-month wave of sunspot activity with that of cosmic-ray intensity, however, does not show any significant correlation.

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Riassunto Si analizzano dati da quattro monitor di neutroni, Climax (1953–1976), Deep River (1964–1977), Mt. Norikura (1957–1983) e Tokyo (1970–1983). Gli spettri di frequenza rivelano picchi alla frequenza di 1 ciclo ogni 16 mesi per tutte le stazioni. Si effettua un'analisi armonica per un periodo di 16 mesi dopo aver eliminato la variazione del ciclo solare a lungo termine. Esiste un accordo generale riguardo alle fasi dei vettori medi per vari monitor di neutroni. L'ampiezza media rispetto a tutte e quattro le stazioni è di 0.41±0.01, mentre risulta superiore per le due stazioni che presentano una rigidità di taglio inferiore alle altre due. Si osserva una crescente coerenza di fase dei vettori in periodi di attività solare minima, rispetto a quella in periodi di attività massima. I grafici della somma rivelano cambiamenti repentini nelle direzioni del vettore d'onda di 16 mesi, corrispondenti all'inversione di polarità del campo magnetico del Sole. Il confronto di un'onda di 16 mesi dell'attività delle macchie solari con quella dell'intensità dei raggi cosmici, tuttavia, non mostra nessuna correlazione significativa.

     

Observation results of relativistic electrons detected by Fengyun-1 satellite and analysis of relativistic electron enhancement (REE) events

The space particle component detector on Fengyun-1 satellite which works at the sun-synchronous orbit of about 870 km altitude has detected relativistic electrons for a long time. In comparison with the SAMPEX satellite observations during 1999–2004, the relativistic electron data from Fengyun-1 satellite from June 1999 to 2005 are used to analyze the relativistic electron enhancement (REE) events at the low earth orbit, and the possible correlation among REE events at the low earth orbit, high-speed solar wind and geomagnetic storms is discussed. The statistical result presents that 45 REE events are found in total during this time period, and the strong REE events with the maximum daily average flux > 400 cm⁻²·sr^t-1·s⁻¹ occur mostly during the transition period from solar maximum to solar minimum. Among these 45 REE events, four strong REE events last a longer time period from 26-to 51-day and correlate closely with high speed solar wind and strong geomagnetic storms. Meanwhile, several strong geomagnetic storms occur continuously before these REE events, and these continuous geomagnetic storms would be an important factor causing these long-lasting strong REE events. The correlation analysis for overall 45 events indicates that the strength of the REE events correlates with the solar wind speed and the strength of the geomagnetic storm, and the correlation for strong REE events is much stronger than that for weak REE events.     

Detection of solar neutrons by ground-based neutron monitors

Summary The analysis of the Rome NM-64 data, performed on the occasion of 8 solar flares accompanied by gamma-bursts and 10 solar flares accompanied by large X-ray fluxes, shows that the solar energetic neutron events could be detected by ground-based stations particularly when they are located at mountain altitude and middle-low latitudes. Suggestions for improving the neutron monitor efficiency for detecting solar neutron events are given. Paper presented at the 2^o Convegno Nazionale di Fisica Cosmica, held at L'Aquila, 29 May-2 June 1984.     

Neutrons and antiprotons in ultrahigh-energy cosmic rays

The neutron fraction in the very high-energy cosmic rays near the Greisen-Zatsepin-Kuzmin (GZK) cutoff energy is analyzed by taking into account the time dilation effect of the neutron decays and also the pion photoproduction behaviors above the GZK cutoff. We predict a non-trivial neutron fraction above the GZK cutoff and a negligibly small neutron fraction below. However, there should be a large antiproton fraction in the high-energy cosmic rays below the GZK cutoff in several existing models for the observed cosmic-ray events above and near the GZK cutoff. Such a large antiproton fraction can manifest itself by the muon charge ratio μ⁺/μ^- in the collisions of the primary nucleon cosmic rays with the atmosphere, if there is no neutron contribution. We suggest to use the muon charge ratio as one of the information to detect the composition of the primary cosmic rays near or below the GZK cutoff.     

On possible role of neutrons in appearance of delayed muons in MUON-T setup at the Tien Shan high-altitude station

The MUON-T setup operated at the Tien Shan high-altitude station of the Lebedev Physical Institute (3340 m above sea level) at a soil depth of ∼10 m (∼20 m m.w.e.). Muons with delay times of 30–150 ns with respect to the extensive air shower front were observed at this setup. Calculations showed that delay times of relativistic muons, taking into account their deviations in the geomagnetic field, do not exceed ∼30 ns. To elucidate the possible role of neutrons in the appearance of delayed events due to the n-p reaction in the plastic scintillator material, the problem of neutron transport in a medium with a density of 2 g/cm³ and a humidity of 10% was solved by the Monte Carlo method. Calculations for a point source of neutrons with energies of 5, 10, and 20 MeV (such neutrons can be generated, in particular, in cascades in soil from hadrons of the shower core) showed that the neutron flux decreases more than by a factor of 10⁴ at a distance of 2.8 m of soil from the source. Neither neutron crosses the boundary of 3m at the total statistics of 3 · 10⁵ events. Since the MUON-T setup is at a depth of 10 m, it is clear that neutrons from the atmosphere and soil upper layer are absorbed, scattered, and do not reach the detector. Thus, the formation of delayed muons in the MUON-T setup cannot be explained by these neutrons.     

Proton distribution at low altitudes in near-equatorial latitudes according to satellite experiments: The dynamics of proton fluxes

The data obtained on the ACTIVE, SAMPEX, and TIROS-N satellites are used to study the dynamics of low-energy (from tens of keV to several MeV) proton fluxes in the region of the geomagnetic equator (L < 1.15) at low altitudes (up to 1000 km). The dependence of the fluxes on the local magnetic time is presented. A number of magnetic disturbances in November–December 1978 are analyzed to illustrate the dependence of the flux on the geomagnetic activity level. The results obtained allow the conclusion that the ring current is one of the main sources of protons at low altitudes in near-equatorial latitudes.     

Measurement of the K α to L α and K β to L β intensity ratios of seven elements in the atomic number range 52≤ Z ≤62 using photoionization at 59.5 keV1

The Kα to Lα and Kβ to Lβ intensity ratios of seven elements have been measured following photoionization at 59.5 keV by using a Si (Li) detector (FWHM=155 eV at 5.96 keV). The intensity ratios were determined by measuring K and L x-rays emitted from a standard target of a given element. The theoretical values of the Kα to Lα and Kβ to Lβ intensity ratios were calculated using theoretically tabulated values of shell/subshell photoionization cross sections, fluorescence yields, Coster-Kronig transition probabilities, and radiative decay rates for ηKLi≠ and ηKLi=0. The measured values are in good agreement with theoretical results. From Optika i Spektroskopiya, Vol. 97, No. 2, 2004, pp. 186–189. Original English Text Copyright ? 2004 by A. Kü?ük?nder, S?ğüt, E. Kü?ük?nder, Büyükkasap. This article was submitted by the authors in English.     

Search for the NN → 6q phase transition in the np-polarized measurements at T kin = 1–6 GeV

The measurements of np-spin observables at 0° have been performed for the first time on the Delta-Sigma experimental facility of LHE JINR up to P _n = 4.5 GeV/c using the monochromatic neutron beam. They include detailed measurements of the Δσ _L(np) spin differences and the study of the np → pn elastic charge-exchange process. In the Δσ _L(np) and −Δσ _L(I = 0) energy dependencies over the energy region T_kin = 1.2–3.7 GeV the peculiarity at 1.8 GeV was observed. Such energy behavior was predicted by the QCD approach as a signal of the NN → 6q phase transition. For the exhaustive investigation of this effect it is necessary to measure the energy dependence of the complete set of np observables with both longitudinal (L) and transverse (T) polarizations of the neutron beam and proton target. This will allow Direct Reconstruction of all three NN forward Scattering Amplitudes (DRSA) to be performed, and the observed peculiarity to be checked around T_kin = 1.8 GeV and at the higher energies using the Argand diagrams method.     

Neutrino backgrounds in the Kolar Gold Field nucleon decay experiment

The neutrino events recorded in the Kolar Gold Field Nucleon Decay detector are analysed here. It is shown that there is good agreement between the observations and the estimates based on the intensities of atmospheric neutrinos and interaction cross-sections of neutrinos available from accelerator experiments. In the context of the search for proton decay, we show that the low energy (<2 GeV) neutrino events, which would provide the main background, are suppressed at thekgf site since it is situated near geomagnetic equator, where the geomagnetic cut-off rigidities are high. A comparison of the predicted characteristics ofv-induced events with thekgf observations shows that, within the statistical accuracy of the present data, the signal due to nucleon decay stands out distinctly within thev-induced background.     

Harmonics of Daily Variations in Cosmic-Ray Intensity

The high/low amplitude anisotropic wave-train events (HAE/LAE) in cosmic-ray intensity have been investigated during the period 1991-94, using the neutron monitor data for different latitudes. In all, 16 HAE and 13 LAE cases have been studied. An inter-comparison of the first three harmonics during these events has been made so as to understand the basic reason causing the occurrence of these types of events. It has been observed that the phase of diurnal anisotropy shifts towards earlier hours for HAEs; similarly, it shifts towards earlier hour as compared to 18-Hr direction for LAEs. For semi-diurnal anisotropy phase remains statistically the same for both HAE as well as for LAE. Further in case of tri-diurnal anisotropy phase is evenly distributed for both types of events. The interplanetary magnetic field and solar-wind plasma parameters during these events are also investigated. It has been also observed that HAE/LAEs are weakly dependent on solar-wind velocity.     

Large transverse momenta in nuclear interaction at E 0 > 1016 eV detected in stratosphere

A gamma-hadron superfamily of cosmic-rays created by a primary cosmic-ray particle with energy above 10¹⁶ eV was detected at an altitude of 30 km by a stratospheric balloon-borne emulsion chamber. Being of superhigh energy, this event is the unique example in the world statistics of practically pure nuclear interactions in the energy range unattainable for modern accelerators. The present analysis allowed one to estimate the interaction height above the chamber and transverse momenta of the secondaries produced in the interaction. The mean value of transverse momenta appears to be very large (〈p _t〉 > 2.5 GeV/c). The text was submitted by the authors in English.